Cathode for thermionic valves



Feb. 4, 1936. A. HASLAUER CATHODE FOR THERMIONIC VALVES Filed April l4, 1934 IN VEN TOR BY dwf kwam;

A TTORN 'LTI Patented Feb. 4, 1936 UEED STATES eArENT OFFICE 3 Claims.

This invention relates, generally, to thermionic valves or vacuum tubes, and the invention has reference, more particularly, to a novel construc- A tion of cathode for use in such valves or tubes.

Heretofore, in certain types of thermionic or Vacuum tubes such as the {IY-227 tube, the usual cathode iilament has been replaced by an indirectly heated cathode consisting of an oxidecoated metal cylinder which is heated by an internal iilament insulated from the cylinder. The iilament is usually tungsten and may be operated with alternating current, the uctuations in temperature o-f the filament with each alteration of the current being prevented from varying the substantially uniform temperature of the cylinder owing to the thermal inertia of the insulating material and of the cylinder.

These cylinders, as heretofore constructed, have generally been formed from a narrow strip of thin sheet metal, the side edges of the strip being brought together in abutting or slightly overlapping relation when forming a cylinder. These overlapping edges were not secured together, so that the cylinder was relatively weak and easily deformed when handled, as when installing the same in a thermionic tube. .Som-etiines these cylinders were made of drawn seamless tubing, but such seamless tubing in practice was of varying thickness and did not possess uniform electrical properties nor uniform strength throughout. These cathode cylinders were supported upon the desired tube posts, by the use of tabs or strips oi metal, each of these tabs or metal strips being secured at one of its ends as by welding to the tube post and at its other end as by welding to the cathode cylinder.

Not only was the attaching of the tab to the cathode cylinder a delicate operation, necessitating great care to avoid deforming the small and easily bent cylinder as well as increasing the labor involved in making the thermionic tube, but an indentation or surface irregularity was positioned at the point of attachment of the tab to the N cylinder, thereby interferring with the electrical the cathode.

(Cl. Z50-27.5)

greatly lessened and its action rendered uncertain.

The principal object of the present invention is to provide a novel construction of cathode cylinder that is exceedingly strong and rigid, thereby enabling the same to be handled without injury thereto, the same retaining its true cylindrical shape when installed and throughout the life of the thermionic valve, thereby lengthening the life of such valve and enhancing the reliability of its action.

Another object of the present invention lies in the provision of a novel cathode of the above character that is so constructed and arranged as to provide a locked joint extending the full length of the cylinder or tube in place of the attached lap joint heretofore used, the said joint comprising four thicknesses of metal and serving to greatly stiifen the cylinder so that the strength thereof is considerably greater than that of a seamless tube.

Still another object of the present invention is to provide a novel cathode of the above character wherein the locked joint is continued beyond the end of the cylinder, thereby providing a rigid and integral tab or tongue for connecting the cylinder to the tube post.

Other objects of this invention, not at this time more particularly enumerated, will be clearly understood from the following detailed description of the same.

The invention is clearly illustrated in the accompanying drawing, in which:

Fig. 1 is a view in front elevation with parts broken away of a thermionic valve provided with the novel cathode of this invention.

Fig. 2 is an enlarged, fragmentary rear sectional view showing the cathode and associated parts.

Fig. 3 is an enlarged View in side elevation of the novel cathode cylinder.

Fig. 4 is .an enlarged view in front elevation of the cathode cylinder.

Fig. 5 is a vertical view taken along line 5--5 of Fig. 4 looking in the direction of the arrows.

Fig. 6 is an enlarged sectional View taken along line @-6 of Fig. 4 looking in the direction of the arrows.

Fig. 7 is a schematic view in end elevation showing the manner of forming the novel cathode cylinder,

Fig. 8 is a schematic perspective view showing the manner of interlocking the joint folds, and

Fig. 9 is a schematic fragmentary perspective View showing the manner of forming the tab.

as sheet nickel.

Similar characters of reference are employed in said views, to indicate corresponding parts.

Referring now to the said drawing, the reference numeral I designates a thermionic valve or vacuum tube having a bulb 2 and base 3 provided with contact prongs 4. Within the bulb 2 there is the usual glass supporting neck 5 carrying upstanding spaced posts 6 and 'I. A plate of the Screen type having a cylindrical main or active portion 8 and a dat attaching portion 9 is attached to post 6 as by spot welding. Extending concentric-ally within the plate 8 is the helical wire grid I0, the said grid being supported upon a bracket I I that is carried by post 'I.

Positioned to extend centrally within grid I0 is the novel cathode I 2 of this invention, the said cathode being of cylindrical shape and having an integral tab or tongue i3 projecting downwardly and outwardly from the lower end of the same for attachment, as by welding, t0 a post I5 carried by neck 5. The upper end portion of cathode I2 extends through a conforming aperture I6 provided in a mica or other electrical insulating support I? that is fixedly carried by the upper end portions of posts 6 and `I.

Porcelain or other heat resisting electrical insulating material I8 is xedly contained within the hollow interior of cathode I2 and has two longitudinal bores or apertures I9 and I9 extending therethrough for receiving the inverted U-shaped filament wire 20 that has its end portions welded to posts 2I and 22 carried by neck 5.

The cathode I2 (see especially Figs. '7 to 9) is formed from a strip I2 of thin sheet metal such One end portion of the strip I2 is illustrated as provide-d with a central tangular cut out or recess 28, (see Fig. 9) thereby forming two tongues 29 at opposite sides of this recess.

The opposite longitudinally extending side edge portions 23 and 24 of the metal strip I 2 are folded over toward opposite surfaces of the body of the strip, thereby forming narrow recesses or pockets 25 and 2G between these side edge portions and the strip body. The tongues 29 are substantially equal in width to twice the width of the folded over edge portions 23 and 24. The strip I2 is then curled or bent as shown in dotted lines in Fig. 'l so as to bring the side edges of the strip toward each other. The side edge portion 23 is then entered or moved into the recess 25, while the opposite side edge portion 24 is simultaneously entered or moved into the reces-.fy 25. The folded or doubled over side edge portions 23 and 24 are new interlocked and the assembled lock joint 3Q is compressed in a radial direction thereby permanently locking the side edge portions of the strip I2 together and forming the cathode cylinder I2. Preferably, the outer surface of the cathode I2 is truly cylindrical, as especially shown in Fig. 6, thereby pro- Viding for ideal electrical interaction between the cathode and the cylindrical plate 8 and grid In forming the cathode cylinder, the outer side edge portions 23 and 24 of the tongues 2S are also interlocked, thereby forming the integral tab I3 which, in eifect, is a continuation of the lock joint 30 beyond the end of the cathode cylinder. This tab I3 may be turned outwardly as especially shown in Figs. 3 and 5, if necessary, to enable the ready welding of the same to the post I5.

Owing to the manner of forming the lock joint 30 and to the fact that this joint employs four thicknesses of metal, the same is very strong and serves to greatly strengthen and stiffen the cathode cylinder. From an engineering standpoint, the joint 30 serves to substantially increase the moment of inertia of the cross-sectional area of the cylinder, thereby correspondingly increasing the resistance of the cylinder to bending and distorting forces. The folded over edge portions 23 and 2li being integrally connected to the body of the cylinder, causes the joint and cylinder body to act as a substantially integral structure and without possibility of relative movement. The tab I3, being a continuation of the joint 30 is hence very strong and serves to definitely and permanently position the cathode cylinder as desired with respect to the grid I 0 and plate 8. Since this tab is not welded to the cathode cylinder, there is no distortion of the cylinder due to the welding process, and the labor involved in assembling the cathode in the tube is greatly lessened.

As many changes could be made in the above construction and many apparently widely diierent embodiments of this invention could be madc without departing from the scope thereof, as defined by the following claims, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be A interpreted as illustrative and not in a limiting sense.

I claim:

l. In a thermionic valve having a supporting post, a cathode comprising, a cylinder formed u from a strip of sheet metal, the side edges of the strip being interlocked together, thereby providing the cylinder with a longitudinal reenforcing joint, said joint being continued beyond the one end of said cylinder to form a tab for connection f to said supporting post.

2. In a thermionic valve having a supporting post, a cathode comprising, a cylinder formed from a strip of sheet metal, the side edge portions of the strip being folded toward opposite surfaces of the strip and interlocked one with another, thereby providing the cylinder with a longitudinal reenforcing joint, said joint being continued beyond the end of said cylinder to form a tab for connection to said tube supporting post.

3. In a thermionic valve having a supporting post, a cathode comprising, a cylinder formed from a strip of sheet metal having a cut out opening in one end portion thereof, the side edge portions of the strip being folded toward opposite surfaces of the strip and interlocked one with another, thereby providing the cylinder with a longitudinal reenforcing joint, the portions of s-aid sheet metal strip at the sides of said cut out opening forming a continuation of said joint beyond the end of said cylinder, said joint continuation serving as an attaching tab.

ADOLF HASLAUER. 

